Ease of Use

PA Server Monitor

Adding new servers? Copy-paste a list of servers, or do Discovery, and let Smart Config take care of it.

Nagios

"the duplicate configuration on each server soon becomes tedious and unmanageable. There are other alternatives such as mod_gearman but in my opinion these lack the intelligence to be effective.
The ability to have centralised configuration in a distributed setup isn't currently supported by Nagios"

Requires installing and configuring platform-specific agent on each monitored server

PA Server Monitor

One monitor watches many services, with a few clicks.

Tedious to configure monitoring for many services.

Spiceworks

Nagios

Customer Support Level

PA Server Monitor

Nagios

Spiceworks

New Relic

PRTG

Documentation

Support Forum

Email Support

Phone Support

“I'm working in this industry for 15 years now, but I can hardly remember working with a software company with a support like you have. You listen and new features come really fast. I'm deeply impressed by your support and now have the feeling we made the 100% right choice to choose PA Server Monitor.”Hanjo P, Pohlmann & Dimai GbR, Germany

“You guys are incredible, Your product is great and with support like this it only continues to improve! I have been and will continue to recommend PA Server Monitor to industry colleagues. Keep up the good work.”Jeremy B, Challenger, Australia

Data Security

PA Server Monitor

All of your data, configuration, network layout, server and network credentials, etc. stays on your hardware. Nothing is sent to the cloud.

Spiceworks

Sends your network data to cloud servers

New Relic

Sends your network data to cloud servers

MAXfocus

Sends your network data to cloud servers

PA Server Monitor

Stays up to date on security advisories. Updated OpenSSL to patch POODLE vulnerability in 2014, almost two years before Spiceworks.

Spiceworks

PA Server Monitor

Any security vulnerabilities are fixed immediately, before any additional features or customer requests.

In addition, we have a 'no known bugs' policy, meaning all bugs are fixed before additional work on the product continues.

Nagios

Known vulnerability in core NPRE module from April 2014 still not fixed.
Source: http://legalhackers.com/advisories/nagios-nrpe.txt